Z,
How much worse would P4 yields have to be than PIII/Athlon/Duron to explain the lower number of processors/fab?
Before you go into yields, you have to look at the die size, which tells you how many chips fit on a wafer. The die size of P4 is 217 mm^2, which is about 2x the die size of Piii/Athlon/Duron.
Let me show you an example that is an extremely rough approximation:
The total area of the wafer is approximately 30,000 mm^2. Suppose P4 is 200 mm^2, you get theoretical maximum of 150 good die. But with 100 mm^2 Piii/Athlon/Duron, the theoretical maximum is 300 good die.
So you start with 150 potential good die or P4 vs. 300 Piii/Athlon/Duron, and you multiply this number by a factor called yield, which is related to defect density.
So let's go back to my original example of comparing P4 and Piii, since they are on the same process. One thing you can be sure about is that the yield of Piii will be higher than that of P4. Let me use just a WAG numbers, that may or may not be close to reality. Suppose Piii yield is 70%, and P4 yield (which has to be lower) is 60%.
Multiplying good die candidates x yield:
P3 ..... 300 x 0.7 = 210
P4 ..... 150 x 0.6 = 90
So when decides to use the wafer for Piii, they end up with 210 processors made out of this wafer that will be available for sale, but if they decide to use it for P4, they will end up with only 90 processors.
This should give you some idea about this shortage. Under normal circumstances, Intel would have left P4 to be low volume, high priced product, during the initial stages of its life. During these initial stages of the life of the processor (before the first shrink), Intel would have relied on the previous generation processor to satisfy most of the volume.
But because the previous generation of Intel product (Piii) is outgunned by the competition, Intel was forced to accelerate the production of the next generation of the product (P4) to reach the volume necessary for the chip to become mainstream. But as my example illustrated, to get 1 P4, Intel has to sacrifice at least 2 Piiis.
Joe |
